This invention relates generally to devices for filtering and separating fluids. More particularly, the present invention relates to fuel filters for removing foreign particles and separating water from fuel and fuel supply systems of an internal combustion engine.
The absence of high standards and quality control in diesel fuel supplies dictates that an effective fuel filter be incorporated into the fuel supply system of the diesel engine. It is not uncommon for diesel fuel to have significant quantities of abrasive particles and water. The abrasive particles present the potential for permanent damage to components of the fuel injection pump. In addition, the abrasive particles can adversely effect the performance of the pump by destroying the ability of the fuel injection pump to precisely meter and deliver fuel at high pressures. The presence of water in the diesel fuel supply can cause corrosion of engine components, and during freezing conditions, can result in interruption of the fuel injection system and/or seizure of moving components.
Fuel filters commonly employ a disposable filter cartridge which is replaced at pre-established intervals of filter usage. There are a wide variety of fuel filter cartridge configurations and orientations. The replaceable cartridge is conventionally secured to the base and/or locked to the base by a locking mechanism which is releasable to allow for removal of the cartridge for replacement purposes.
In U.S. Pat. No. 5,017,285, which is assigned to the assignee of the present invention, one disclosed inverted fuel filter assembly employs a base which mounts to the vehicle and a disposable filter cartridge which is suspended directly below the filter base. The cartridge has a housing constructed of a pair of cup-like sections which are joined along a roll seam. The roll seam functions as a retaining shoulder for engagement by a collar which threads to the base to retain the collar in position. The disposable cartridge preferably houses a dual stage filter. The lower portion of the housing forms a sump which collects water separated by at least one of the filter elements. A central axial opening at the bottom of the cartridge housing receives a drain cock. The drain cock threads into an insert which is pressed into the interior lower end of the cartridge housing. Water may be drained from the cartridge by opening the drain cock.
For certain applications, it is highly desirable that a drain bowl for the separated water be provided in conjunction with the fuel filter. The drain bowl functions to provide additional capacity for retaining the separated water. In addition, the drain bowl may be constructed of transparent materials which allow for ready exterior inspection of the water level so that the water may be drained from the bowl before maximum capacity is reached, and the effectiveness of the water separating properties of the fuel filter may be monitored.
The conventional employment of a drain bowl in conjunction with a fuel filter cartridge has essentially involved integrating the somewhat bulky drain bowl structure with the filter assembly or the filter cartridge. Naturally, the implementation of an effective fluid seal and the provision of mounting structure having a structural integrity sufficient to support the bowl are requisite to incorporating a drain bowl into the fuel assembly. In some applications, the filter cartridge is significantly modified so that it will directly accept or mount the drain bowl in a permanent fashion.
A problem associated with the use of drain bowls and the use of drain mechanisms for removing the separated water in general is providing a drain passage structure which will produce a sufficient rate of fluid or water flow. Because the filtering and separating functions of the fuel filter are conducted in a closed structure, in practice the draining of separated water from the cartridge housing tends to occur at a very low rate. The low drain rate can be attributed in part to the relatively small conventional drain openings, the surface tension of the separated water in the vicinity of the drain openings, and the unfavorable pressure differentials exerted on the separated water. In a number of applications which employ a drain bowl, the passage of separated water to the drain bowl is very inefficient and/or the draining of the separated water from the bowl or the cartridge is problematical.